Recently, in our country, it has been shifted from heavy industry to light industry in which specialty products are manufactured and dealt. The number of situations where food products, medical products, cosmetics, automotive parts and the like are dealt is increasing, and needs for conveyance of lightweight objects in which the above products are dealt between processes or in distribution are on the rise.
Needs of various users such as a machine length and a belt width regarding a conveyor for conveyance of lightweight objects in which the lightweight objects as described above are dealt have been conventionally changed depending on a conveyance object or a conveyance line of the conveyor, and in order to serve the needs promptly at a low price, parts are used in common. However, since the parts are used in common, a drive unit having the most complicated mechanism is always provided in accordance with the largest belt width among belt widths which are set in common, which leads to increase in size of the parts, and increase in the number of parts.
In a belt conveyor device which conveys a conveyance object, an endless belt is laid between a tail pulley disposed at an end portion on an upstream side in a conveyance direction and a head pulley disposed at an end portion on a downstream side in the conveyance direction, and there is provided a drive device for making the endless belt travel on a return route side of the endless belt (refer to Patent Document 1). The drive device is generally disposed at a position in the vicinity of the head pulley on the return route side of the endless belt laid between the head pulley and the tail pulley, or the like.
Each of FIG. 8 and FIG. 9 illustrates one example of a drive device used for a belt conveyor device. In the drive device 100, a drive motor 101 and a drive pulley 102 are respectively fixed to a frame 103 so that an axial direction of an output shaft 101a of the drive motor 101 being a driving force source and an axial direction of a rotary shaft 102a of the drive pulley 102 become parallel, and a snub pulley 110 is positioned between the drive motor 101 and the drive pulley 102. By designing as above, an endless belt which is wound around the drive pulley 102 is turned back by the snub pulley 110, so that the drive motor 101 can be positioned outside the endless belt, resulting in that a power transmission part can be freely arranged. Note that in the drive device 100 illustrated in FIG. 8 and FIG. 9, the frame 103 is formed by combining plural members 103a, 103b, 103c, 103d, and 103e, in order to support both ends of the rotary shaft 102a of the drive pulley 102 and to support the drive motor 101 on a machine side. Further, in the drive device 100, the drive pulley 102 is attached to side frames 103a, 103b which form the frame 103, in a state where both end portions of the rotary shaft 102a of the drive pulley 102 are pivotally supported by bearing members 104, 105. Accordingly, the side frames 103a, 103b have to be made of a metal material with large rigidity, in order to receive force applied to the bearing members 104, 105. The drive motor 101 and the drive pulley 102 are disposed so that the axial direction of the output shaft 101a of the drive motor 101 and the axial direction of the rotary shaft 102a of the drive pulley 102 become parallel, sprockets 107, 108 are fixed to the output shaft 101a of the drive motor 101 and the rotary shaft 102a of the drive pulley 102, respectively, and a chain 109 is wound around the sprockets 107, 108, to form the power transmission part, thereby transmitting driving force of the drive motor 101 to the drive pulley 102. A change of direction of the driving force is made at the power transmission part, and also from that point, the side frame 103b is required to be made of the metal material with large rigidity. Further, in the drive device 100, the snub pulley 110 and a take-up pulley 111 which turn back the front side of the endless belt toward the drive pulley 102 on the return route side of the endless belt are provided, and in addition to that, a safety cover 112 for the snub pulley 110, a fixing key plate 113 for the sprocket 108, and the like are also provided. Besides, there are also provided large-sized covers 114, 115, 116, and 117, which cover the outer part of the side frame 103, in order to cover the drive motor 101 and the respective pulleys assembled to the frame 103.
Further, in order to suppress occurrence of scratch on an outer surface (conveyance surface) of the belt and to secure a scratch-free belt surface over a long period of time in a manner that a scratch occurs only in a predetermined width close to one side portion in a width direction of the outer surface of the belt, and no scratch occurs on the other portion, there is also disclosed, as another drive device for a belt conveyor, a drive device for a belt conveyor in which a drive mechanism is positioned close to one side in the width direction of the belt and a short cylindrical drive pulley is disposed inside the belt, and a pinch roller to press the endless belt against the drive pulley, and a guiding unit supporting the belt in a state similar to a winding state of the drive pulley on the opposite side in the belt width of the line on which the drive mechanism is positioned (refer to Patent Document 2).